<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="../bootstrap-5.1.3-dist/css/bootstrap.css">
  <script src="../bootstrap-5.1.3-dist/js/bootstrap.js"></script>
</head>
<style>
  div {
    width: 200px;
    height: 50px;
  }
</style>

<body class="container">
  <h3 class="mb-4">响应式的边距</h3>
  <div class="mx-auto me-sm-2 border border-primary" style="width:150px">mx-auto me-sm-2</div>
</body>

</html>